Elevation of night-time temperature increases terpenoid emissions from Betula pendula and Populus tremula

Abstract

Volatile organic compounds (VOCs) are expected to have an important role in plant adaptation to high temperatures. The impacts of increasing night-time temperature on daytime terpenoid emissions and related gene expression in silver birch (Betula pendula) and European aspen (Populus tremula) clones were studied. The plants were grown under five different night-time temperatures (6, 10, 14, 18, and 22 °C) while daytime temperature was kept at a constant 22 °C. VOC emissions were collected during the daytime and analysed by gas chromatography–mass spectrometry (GC-MS). In birch, emissions per leaf area of the C11 homoterpene 4,8-dimethy1-nona-1,3,7-triene (DMNT) and several sesquiterpenes were consistently increased with increasing night-time temperature. Total sesquiterpene (SQT) emissions showed an increase at higher temperatures. In aspen, emissions of DMNT and β-ocimene increased from 6 °C to 14 °C, while several other monoterpenes and the SQTs (Z,E)-α-farnesene and (E,E)-α-farnesene increased up to 18 °C. Total monoterpene and sesquiterpene emission peaked at 18 °C, whereas isoprene emissions decreased at 22 °C. Leaf area increased across the temperature range of 6–22 °C by 32% in birch and by 59% in aspen. Specific leaf area (SLA) was also increased in both species. The genetic regulation of VOC emissions seems to be very complex, as indicated by several inverse relationships between emission profiles and expression of several regulatory genes (DXR, DXS, and IPP). The study indicates that increasing night temperature may strongly affect the quantity and quality of daytime VOC emissions of northern deciduous trees.

Leaf Volatile Emissions of Betula pendula during Autumn Coloration and Leaf Fall

“…Inducible terpenes and photosynthesisrelated monoterpenes were typical of green foliage emission profiles, and GLVs typical of senescing foliage. Our first hypothesis that a reduced proportion of costly photosynthesis-related VOCs will be emitted by senescing foliage is supported by our results, which show that VOCs known to be induced by herbivores (Vuorinen et al, 2007;Blande et al, 2010) or abiotic stress (Ibrahim et al, 2010) like DMNT, linalool, and (E)-β-ocimene are emitted by green leaves, but not by mostly yellow foliage. These inducible compounds can be found in small amounts (emission rates below 50 ngg −1 DW h −1 ), in the emissions of actively growing intact B. pendula saplings (Vuorinen et al, 2005).…”

“…Fungal pathogen infection, however, may increase (E)-β-ocimene emission by 30-fold, and chewing herbivore feeding increase the emission of these compounds by more than 10-fold (Vuorinen et al, 2007). We did not find the sesquiterpene (E,E)-α-farnesene in the emission profile, although during summer it is emitted abundantly by many B. pendula genotypes (Vuorinen et al, 2005(Vuorinen et al, , 2007Ibrahim et al, 2010) and is a typical herbivore-induced VOC in several plant species (e.g., Blande et al, 2007;Pinto et al, 2007). However, α-pinene and β-pinene-light and photosynthesis-related monoterpenes (Hakola et al, 2001;Loreto et al, 2004)-were emitted from leaves in the last stage of senescence, which is against our hypothesis.…”

“…Each shoot was enclosed in a pre-cleaned (oven-heated 120°C, 1 hr) multi-purpose polyethylene terephthalate (PET) cooking bag, (vol. 3 l, Look, Terinex Ltd., UK) (Ibrahim et al, 2010). The bags were fastened carefully to the shoot bark with gardening wire with care taken not to damage any foliage.…”

Sensitivity of Norway spruce physiology and terpenoid emission dynamics to elevated ozone and elevated temperature under open-field exposure

“…Elevated temperature is known to affect expression of DXR and DXS in poplar (Populus trichocarpa), European aspen and silver birch (B. pendula), although relationship to emission rates is not straightforward (Wiberley et al, 2009;Ibrahim et al, 2010). In this experiment elevated temperature decreased the expression of PaDXS2B, but the effect on PaDXR was of lower magnitude.…”

Can the capacity for isoprene emission acclimate to environmental modifications during autumn senescence in temperate deciduous tree species Populus tremula?

“…While in mid-season, average temperature of preceding days has been proven to be the best predictor of E S (Geron et al 2000;Guenther et al 2006;Pétron et al 2001;Sharkey et al 1999;Wiberley et al 2008), minimum temperatures may constitute a stronger stress factor during senescence. In fact, enhancement of isoprene synthase activity by low night temperatures has been reported (Ibrahim et al 2010). On the other hand, as all chemical reactions run faster at higher temperature, formation of ROS can depend on temperature per se not necessarily on minimum temperature.…”